This project concerns the development of a radioimmunoassay with which to evaluate patient response to therapy in multiple myeloma and to chart the tumor growth kinetics in this disease. This will be done by quantitating the levels of myeloma protein in serum and of Bence Jones protein in serum and urine, in a large population of patients over the course of their disease, from pretreatment to relapse. The pattern of tumor growth, remission and regrowth will be analyzed and applied to: (1) Evaluate the nature of patient response to therapy and escape from remission, (2) construct mathematical models that depict the growth kinetics of myeloma cells e.g., an exponential, Gompertzian, etc., (3) estimate tumor halving time, doubling time, and time required for proliferation of a single tumor cell to a mass sufficient to manifest the clinical syndrome, and (4) eventually, monitor new therapeutic modalities.